Sidelink synchronization signal block (s-ssb) design

Abstract

A method of synchronization for sidelink communications can include synchronize to a synchronization source at a user equipment (UE) to determine a frame timing for sidelink communications, and transmitting a sidelink synchronization signal block (S-SSB) according to the frame timing. When the synchronization source is a global navigation satellite system (GNSS), a slot number can be determined according to a GNSS timing and a subcarrier spacing. In one embodiment, the slot number can be determined based on a function of μ,Tcurrent, Tref and offsetDFN.

1 . A method, comprising:
 synchronizing to a synchronization source at a user equipment (UE) to determine a frame timing for sidelink communications; and   transmitting a sidelink synchronization signal block (S-SSB) according to the frame timing,   wherein when the synchronization source is a global navigation satellite system (GNSS), the determining the frame timing includes determining a slot number based on a GNSS timing and a subcarrier spacing.   
     
     
         2 . The method of  claim 1 , wherein the S-SSB includes a physical sidelink broadcast channel (PSBCH) that carries information of the slot number. 
     
     
         3 . The method of  claim 1 , wherein the S-SSB includes a PSBCH demodulation reference signal (DMRS) sequence that is generated with a time domain S-SSB transmission resource indicator as an initialization value. 
     
     
         4 . The method of  claim 1 , wherein the S-SSB has a PSBCH DMRS resource element (RE) mapping of a fixed RE location with respect to different sidelink synchronization signal (SLSS) identifier (ID). 
     
     
         5 . The method of  claim 1 , wherein the S-SSB includes sidelink primary synchronization signal (S-PSS) symbols of a S-PSS, sidelink secondary synchronization signal (S-SSS) symbols of a S-SSS, and PSBCH symbols of a PSBCH,
 each of the S-PSS symbols, the S-SSS symbols, and the PSBCH symbols has a same total transmission power, and   a transmission power per RE of a PSBCH DMRS in the S-SSB is the same as that of the S-PSS, the S-SSS, or the PSBCH in the S-SSB.   
     
     
         6 . The method of  claim 1 , further comprising:
 transmitting a sequence of S-SSBs that are evenly distributed in time domain in a S-SSB burst set.   
     
     
         7 . The method of  claim 6 , wherein the sequence of S-SSBs are each positioned at the beginning of a 0.5 ms half-subframe. 
     
     
         8 . The method of  claim 1 , wherein determining the slot number based on the GNSS timing and the subcarrier spacing further comprising:
 determining the slot number based on a function of μ,Tcurrent, Tref and offsetDFN,   where μ is an integer indicating a numerology corresponding to a subcarrier spacing, Tcurrent denotes a current time obtained from the GNSS in μs, Tref denotes a reference time in μs, and offsetDFN denotes a timing difference between a wireless network and the GNSS.   
     
     
         9 . The method of  claim 8 , wherein the slot number is determined according to:
   slot number=Floor (0.001*(Tcurrent−Tref−offsetDFN)*2{circumflex over ( )}μ)mod 2{circumflex over ( )}μ.
   
     
     
         10 . An apparatus, comprising circuitry configured to:
 synchronize to a synchronization source at a user equipment (UE) to determine a frame timing for sidelink communications; and   transmit a sidelink synchronization signal block (S-SSB) according to the frame timing,   wherein when the synchronization source is a global navigation satellite system (GNSS), the circuitry is configured to:   determine a slot number based on a GNSS timing and a subcarrier spacing.   
     
     
         11 . The apparatus of  claim 10 , wherein the S-SSB includes a physical sidelink broadcast channel (PSBCH) that carries information of the slot number. 
     
     
         12 . The apparatus of  claim 10 , wherein the S-SSB includes a PSBCH demodulation reference signal (DMRS) sequence that is generated with a time domain S-SSB transmission resource indicator as an initialization value. 
     
     
         13 . The apparatus of  claim 10 , wherein the S-SSB has a PSBCH DMRS resource element (RE) mapping of a fixed RE location with respect to different sidelink synchronization signal (SLSS) identifier (ID). 
     
     
         14 . The apparatus of  claim 10 , wherein the S-SSB includes sidelink primary synchronization signal (S-PSS) symbols of a S-PSS, sidelink secondary synchronization signal (S-SSS) symbols of a S-SSS, and PSBCH symbols of a PSBCH,
 each of the S-PSS symbols, the S-SSS symbols, and the PSBCH symbols has a same total transmission power, and   a transmission power per RE of a PSBCH DMRS in the S-SSB is the same as that of the S-PSS, the S-SSS, or the PSBCH in the S-SSB.   
     
     
         15 . The apparatus of  claim 10 , wherein the circuitry is further configured to:
 transmit a sequence of S-SSBs that are evenly distributed in time domain in a S-SSB burst set.   
     
     
         16 . The apparatus of  claim 15 , wherein the sequence of S-SSBs are each positioned at the beginning of a 0.5 ms half-subframe. 
     
     
         17 . The apparatus of  claim 10 , wherein the circuitry is further configured to:
 determine the slot number based on a function of μ,Tcurrent, Tref and offsetDFN,   where μ is an integer indicating a numerology corresponding to a subcarrier spacing, Tcurrent denotes a current time obtained from the GNSS in μs, Tref denotes a reference time in μs, and offsetDFN denotes a timing difference between a wireless network and the GNSS.   
     
     
         18 . The apparatus of  claim 17 , wherein the slot number is determined according to:
   slot number=Floor (0.001*(Tcurrent−Tref−offsetDFN)*2{circumflex over ( )}μ)mod 2{circumflex over ( )}μ.
   
     
     
         19 . A non-transitory computer-readable medium storing instructions that, when executed by a processor, cause the processor to perform a method, the method compring:
 synchronizing to a synchronization source at a user equipment (UE) to determine a frame timing for sidelink communications; and   transmitting a sidelink synchronization signal block (S-SSB) according to the frame timing,   wherein when the synchronization source is a global navigation satellite system (GNSS), the determining the frame timing includes determining a slot number based on a GNSS timing and a subcarrier spacing.   
     
     
         20 . The non-transitory computer-readable medium of  claim 19 , wherein determining the slot number based on the GNSS timing and the subcarrier spacing further comprising:
 determining the slot number based on a function of μ,Tcurrent, Tref and offsetDFN,   where μ is an integer indicating a numerology corresponding to a subcarrier spacing, Tcurrent denotes a current time obtained from the GNSS in μs, Tref denotes a reference time in μs, and offsetDFN denotes a timing difference between a wireless network and the GNSS.